Flexible solid electrolyte, all-solid-state lithium battery including the flexible solid electrolyte, and method of preparing the flexible solid electrolyte

ABSTRACT

A flexible solid electrolyte includes a first inorganic protective layer, an inorganic-organic composite electrolyte layer including an inorganic component and an organic component, and a second inorganic protective layer, where the inorganic-organic composite electrolyte layer is disposed between the first inorganic protective layer and the second inorganic protective layer, and the inorganic component and the organic component collectively form a continuous ion conducting path.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Korean Patent Application No.10-2012-0146623, filed on Dec. 14, 2012, and all the benefits accruingtherefrom under 35 U.S.C. §119, the content of which in its entirety isherein incorporated by reference.

BACKGROUND

1. Field

Embodiments of the invention relate to a flexible solid electrolyte, anall-solid-state lithium battery including the flexible solidelectrolyte, and a method of preparing the flexible solid electrolyte.

2. Description of the Related Art

Lithium batteries typically have high voltage and high energy densities,and thus are used in various applications. Devices such as electricvehicles, e.g., a hybrid electric vehicle (“HEV”), plug-in hybridelectric vehicle (“PHEV”) and the like, are desired to be operable athigh temperatures, to charge or discharge a large quantity ofelectricity, and to have long-term usability, such that such devices uselithium batteries having high-discharge capacities and better lifetimecharacteristics.

A lithium battery using liquid electrolyte including a lithium saltdissolved in an organic solvent may be chemically unstable when using anelectrode operating at a high voltage of about 5 volts (V) or greater.In such a lithium battery, the liquid electrolyte may begin to decomposeat a voltage of about 2.5 V or greater, and a leakage may occur suchthat a risk of fire or explosion may be high. Growth potential ofdendrite from the liquid electrolyte may lead to self-discharge oroverheating of the lithium battery.

All-solid-state liquid batteries using a solid electrolyte as a lithiumion conductor are considered relatively stable compared to lithiumbatteries using liquid electrolytes. Unlike lithium batteries usingliquid electrolytes, all-solid-state lithium batteries have no leakageconcerns, and thus may be very safe and have high stability. However,electrolyte materials for the all-solid-state lithium batteries areinherently brittle and not flexible such that the solid electrolyte maydecompose when used along with a lithium anode or a high-voltageelectrode, and ionic conductivity of the solid electrolyte may be lowdue to a high grain boundary resistance.

SUMMARY

Provided are embodiments of a flexible solid electrolyte with highelectrochemical stability, high ionic conductivity, and flexiblecharacteristics.

Provided is an embodiment of an all-solid-state lithium batteryincluding the flexible solid electrolyte.

Provided is an embodiment of a method of preparing the flexible solidelectrolyte.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the embodiments described herein.

According to an embodiment of the invention, a flexible solidelectrolyte includes a first inorganic protective layer, aninorganic-organic composite electrolyte layer including an inorganiccomponent and an organic component, and a second inorganic protectivelayer, where the inorganic-organic composite electrolyte layer isdisposed between the first inorganic protective layer and the secondinorganic protective layer, and the inorganic component and the organiccomponent collectively form a continuous ion conducting path.

According to another embodiment of the invention, an all-solid-statelithium battery includes: a cathode; an anode; and a flexible solidelectrolyte disposed between the cathode and the anode, where theflexible solid electrolyte includes: a first inorganic protective layer;an inorganic-organic composite electrolyte layer including an inorganiccomponent and an organic component; and a second inorganic protectivelayer, where the inorganic-organic composite electrolyte layer isdisposed between the first inorganic protective layer and the secondinorganic protective layer, and the inorganic component and the organiccomponent collectively form a continuous ion conducting path.

According to another embodiment of the invention, a method of preparinga flexible solid electrolyte includes: spraying a first inorganicprotective layer forming material on a cathode to form a first inorganicprotective layer; spraying an inorganic-organic composite electrolytelayer forming material on the first inorganic protective layer to forman inorganic-organic composite electrolyte layer; and spraying a secondinorganic protective layer forming material on the inorganic-organiccomposite electrolyte layer to form a second inorganic protective layer.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other features of this disclosure will become more apparentby describing in further detail exemplary embodiments thereof withreference to the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of an embodiment of a flexible solidelectrolyte;

FIG. 2 is a partial enlarged view of the flexible solid electrolyte ofFIG. 1;

FIG. 3 is a schematic view of an embodiment of an all-solid-statelithium battery;

FIG. 4 is a scanning electron microscopic (“SEM”) image showing asurface structure of thin layers formed using aerosol depositionprovided as an Example of a solid electrolyte membrane; and

FIG. 5 is a graph illustrating results of ionic conductivity measurementof the solid electrolyte membrane of the Example shown in FIG. 4.

DETAILED DESCRIPTION

The invention will be described more fully hereinafter with reference tothe accompanying drawings, in which exemplary embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms, and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Likereference numerals refer to like elements throughout.

It will be understood that when an element or layer is referred to asbeing “on,” “connected to” or “coupled to” another element or layer, theelement or layer can be directly on, connected or coupled to the otherelement or layer or intervening elements or layers may be present. Incontrast, when an element is referred to as being “directly on,”“directly connected to” or “directly coupled to” another element orlayer, there are no intervening elements or layers present. Like numbersrefer to like elements throughout. As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items.

It will be understood that, although the terms first, second, third,etc., may be used herein to describe various elements, components,regions, layers and/or sections, these elements, components, regions,layers and/or sections should not be limited by these terms. These termsare only used to distinguish one element, component, region, layer orsection from another element, component, region, layer or section. Thus,a first element, component, region, layer or section discussed belowcould be termed a second element, component, region, layer or sectionwithout departing from the teachings of the invention.

Spatially relative terms, such as “beneath”, “below”, “lower”, “above”,“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation, in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “includes”and/or “including,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

“About” or “approximately” as used herein is inclusive of the statedvalue and means within an acceptable range of deviation for theparticular value as determined by one of ordinary skill in the art,considering the measurement in question and the error associated withmeasurement of the particular quantity (i.e., the limitations of themeasurement system). For example, “about” can mean within one or morestandard deviations, or within±30%, 20%, 10%, 5% of the stated value.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

Embodiments of the invention are described herein with reference tocross-section illustrations that are schematic illustrations ofidealized embodiments (and intermediate structures) of the invention. Assuch, variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, embodiments of the invention should not be construed aslimited to the particular shapes of regions illustrated herein but areto include deviations in shapes that result, for example, frommanufacturing. For example, a region illustrated or described as flatmay, typically, have rough and/or nonlinear features. Moreover, sharpangles that are illustrated may be rounded. Thus, the regionsillustrated in the figures are schematic in nature and their shapes arenot intended to illustrate the precise shape of a region and are notintended to limit the scope of the claims set forth herein.

All methods described herein can be performed in a suitable order unlessotherwise indicated herein or otherwise clearly contradicted by context.The use of any and all examples, or exemplary language (e.g., “suchas”), is intended merely to better illustrate the invention and does notpose a limitation on the scope of the invention unless otherwiseclaimed. No language in the specification should be construed asindicating any non-claimed element as essential to the practice of theinvention as used herein.

Hereinafter, embodiments of the invention will be described in furtherdetail with reference to the accompanying drawings.

According to an embodiment of the invention, a flexible solidelectrolyte includes an inorganic-organic composite electrolyte layerprotected by an inorganic protective layer.

In such an embodiment, the flexible solid electrolyte may have highelectrochemical stability, ionic conductivity and flexibility, and thusmay be employed in, for example, a flexible all-solid-state lithiumbattery.

FIG. 1 is a cross-sectional view of an embodiment of a flexible solidelectrolyte. Referring to FIG. 1, an embodiment of the flexible solidelectrolyte includes a first inorganic protective layer 11, aninorganic-organic composite electrolyte layer including an inorganiccomponent, e.g., an inorganic electrolyte 12, and an organic component,e.g., an organic electrolyte 13, and a second inorganic protective layer14. In such an embodiment, the first inorganic protective layer 11, theinorganic-organic composite electrolyte layer and the second inorganicprotective layer 14 are sequentially stacked on one another.

FIG. 2 is a partial enlarged view of the flexible solid electrolyte ofFIG. 1, illustrating that the inorganic-organic composite electrolytelayer, which is disposed between and protected by the first and secondinorganic protective layers 11 and 14, may function as an ion conductingpath. Referring to FIG. 2, the inorganic component in theinorganic-organic composite electrolyte layer (e.g., the inorganicelectrolyte 12) and the organic component in the inorganic-organiccomposite electrolyte layer (e.g., the organic electrolyte 13)collectively form continuous ion conducting paths such that ionicconductivity is substantially improved. In such an embodiment, theorganic component in the inorganic-organic composite electrolyte layer,e.g., the organic electrolyte 13, may allow the flexible solidelectrolyte to be ductile.

Each of the first inorganic protective layer 11 and the second inorganicprotective layer 14 may include a film that protects theinorganic-organic composite electrolyte layer, and may increasedurability of the flexible solid electrolyte against a higher drivingvoltage of a lithium battery. The first inorganic protective film 11 andthe second inorganic protective layer 14 may include substantially thesame material as each other or different materials from each other. Inan embodiment, the first inorganic protective layer 11 and the secondinorganic protective layer 14 may include at least one of a transitionmetal, a metal in Groups 1, 12, 13, 14, 15 and 16 of the periodic tableof the elements, and compounds of the above-listed metals.

In one embodiment, for example, the first inorganic protective layer 11and the second inorganic protective layer 14 may each independentlyinclude at least one of lithium, magnesium, calcium, strontium, barium,yttrium, lanthanum, titanium, zirconium, hafnium, vanadium, niobium,tantalum, chromium, molybdenum, tungsten, cerium, praseodymium,neodymium, samarium, gadolinium, and yttrium; and oxides, hydroxides,bromides, chlorides, fluorides, sulfides, nitrates, carbonates,sulfates, phosphates, oxalates, and acetates of the above-listed metals.In another embodiment, the first inorganic protective layer 11 and thesecond inorganic protective layer 14 may each independently include atleast one of lithium, calcium, magnesium, yttrium, lanthanum, titanium,zirconium, vanadium, niobium, chromium, cerium, samarium, and oxides,hydroxides, and carbonates of the above-listed metals. In anotherembodiment, the first inorganic protective layer 11 and the secondinorganic protective layer 14 may each independently include ionicliquids of the above-listed metals.

In an embodiment, the first inorganic protective layer 11 and the secondinorganic protective layer 14 may each have a thickness in a range fromabout 1 nanometer (nm) to about 1000 micrometers (μm). In an embodiment,the first inorganic protective layer 11 and the second inorganicprotective layer 14 may each have a thickness in a range from about 10nm to about 100 μm. In such embodiment, the first inorganic protectivelayer 11 and the second inorganic protective layer 14 may be effectivelyductile and effectively protect the inorganic-organic compositeelectrolyte layer.

In an embodiment, the inorganic-organic composite electrolyte layer mayhave a composite structure including the inorganic electrolyte 12 andthe organic electrolyte 13. The inorganic electrolyte 12 may function asa support member of the inorganic-organic composite electrolyte layersuch that stability of the inorganic-organic composite electrolytelayer, which depends on the content of the inorganic electrolyte 12, issubstantially improved. The organic electrolyte 13 may contribute to theductility of the inorganic-organic composite electrolyte layer, andincrease an area thereof. In such an embodiment, the organic electrolyte13 may compensate defects, such as pin holes and cracks, caused by theorganic electrolyte 13, such that interfacial adhesion is substantiallyimproved.

In an embodiment, a weight ratio of the inorganic electrolyte 12 withrespect to the organic electrolyte 13 in the inorganic-organic compositeelectrolyte layer may be in a range of, for example, from about 80:20 toabout 20:80.

In an embodiment, the inorganic-organic composite electrolyte layer mayhave a thickness in a range from about 10 nm to about 1,000 μm. In suchan embodiment, where the inorganic-organic composite electrolyte layermay have a thickness in a range from about 10 nm to about 1,000 μm, theinorganic-organic composite electrolyte layer may be ductile and have asufficiently high ionic conductivity.

In an embodiment, the inorganic electrolyte 12 of the inorganic-organiccomposite electrolyte layer may include at least one of a transitionmetal and metals in Groups 1, 12, 13, 14, 15, and 16 of the periodictable of the elements, and a compound of the above-listed metals. In oneembodiment, for example, the inorganic electrolyte 12 may include atleast one selected from lithium, magnesium, calcium, strontium, barium,yttrium, lanthanum, titanium, zirconium, hafnium, vanadium, niobium,tantalum, chromium, molybdenum, tungsten, cerium, praseodymium,neodymium, samarium, gadolinium and yttrium. In such an embodiment, theinorganic electrolyte 12 may include at least one compound of theabove-listed metals, including oxides, hydroxides, bromides, chlorides,fluorides, sulfides, nitrates, carbonates, sulfates, phosphates,oxalates, and acetates of the above-listed metals.

In one embodiment, for example, the inorganic electrolyte 12 may be atleast one of lithium, calcium, magnesium, strontium, yttrium, lanthanum,titanium, zirconium, vanadium, niobium, chromium, cerium, samarium, andoxides, hydroxides, and carbonates of the above-listed metals.

In one embodiment, for example, the organic electrolyte 13 of theinorganic-organic composite electrolyte layer may include a lithiumconductive polymer and/or an ionic liquid. In such an embodiment, theorganic electrolyte 13 may include an ionic liquid in solid phase.

In such an embodiment, the lithium conductive polymer may include apolymer with a lithium salt, e.g., a blend or complex of the polymer andthe lithium salt. In one embodiment, for example, the polymer of thelithium conductive polymer may be polyethylene oxide (“PEO”),polymethylmethacrylate (“PMMA”), polypropylene oxide, polyvinylidenefluoride (“PVDF”), polystyrene, polyvinyl chloride (“PVC”), polyvinylalcohol (“PVA”), polyacrylonitrile (“PAN”), polyester sulfide,derivatives of the above-listed polymers, and a polymer with an ionicdissociable group. The polymer for the lithium conductive polymer mayinclude at least one of these polymers.

In such an embodiment, the lithium salt of the lithium conductivepolymer may be LiPF₆, LiBF₄, LiSbF₆, LiAsF₆, LiClO₄, LiCF₃SO₃,Li(CF₃SO₂)₂N, LiC₄F₉SO₃, LiAlO₂, LiAlCl₄,LiN(C_(x)F_(2x+1)SO₂)(C_(y)F_(2y+1)SO₂) (where x and y are not the same,and may each independently be an integer of 1 to 20), LiCl, LiI, or acombination thereof, but not being limited thereto. In such anembodiment, an amount of the lithium salt is not specifically limited.In one embodiment, for example, the amount of the lithium salt may be ina range from about 0.1 mole to about 1 mole with respect to 1 mole ofthe polymer.

In an embodiment, the organic electrolyte 13 and the inorganicelectrolyte 12 in the inorganic-organic composite electrolyte layer mayhave a core-shell structure. In such an embodiment, one of the organicelectrolyte 13 and the inorganic electrolyte 12 defines a core of thecore-shell structure, and the other of the organic electrolyte 13 andthe inorganic electrolyte 12 defines a shell of the core-shellstructure. In one embodiment, for example, the inorganic electrolyte 12may define a core of the core-shell structure, and the organicelectrolyte 13 may define a shell of the core-shell structure. In suchan embodiment, where the inorganic-organic composite electrolyte layerhas a core-shell structure, the inorganic-organic composite electrolytelayer may have a substantially dense structure, and thus interfacialresistance therein may be substantially lowered.

The inorganic-organic composite electrolyte layer may further include acommon solid ionic conductor, for example, a common sulfide-basedconductor and/or an oxide-based conductor. In one embodiment, forexample, the common solid ionic conductor may be at least one of Li₃N,lithium super ionic conductor (“LISICON”), lithium phosphorousoxynitride (“LIPON”: Li3-yPO4-xNx, 0<y<3, 0<x<4), thio-LISICON(Li_(3.25)Ge_(0.25)P_(0.75)S₄), Li₂S, Li₂S—P₂S₅, Li₂S—SiS₂, Li₂S—GeS₂,Li₂S—B₂S₅, Li₂S—Al₂S₅, and Li₂O—Al₂O₃—TiO₂—P₂O₅ (“LATP”), but not beinglimited thereto. In such embodiments, any of various solid ionicconductors may be included in the inorganic-organic compositeelectrolyte layer.

According to another embodiment, a method of preparing a flexible solidelectrolyte includes: spraying a first inorganic protective layerforming material on an electrode (e.g., a cathode) to provide, e.g., toform, a first inorganic protective layer; spraying an inorganic-organiccomposite electrolyte layer forming material on the first inorganicprotective layer to provide an inorganic-organic composite electrolytelayer; and spraying a second inorganic protective layer forming materialon the inorganic-organic composite electrolyte layer to provide a secondinorganic protective layer.

In such an embodiment, the flexible solid electrolyte including theinorganic-organic composite electrolyte layer and the first and secondinorganic protective layers may be provided using a spraying process,for example, room-temperature spraying, such as aerosol deposition,thereby suppressing volatilization of lithium, which may occur inhigh-temperature sintering, and fragility of oxides, such that theflexible solid electrolyte prepared thereby has improved flexibility anda large area. In such an embodiment, reduction on an interfacialresistance between the electrodes and the electrolyte membrane or aninterfacial resistance in the electrolyte membrane, which may occurduring the high-temperature spraying process, may be effectivelyprevented.

As used herein, the term “room temperature” is defined as an absolutetemperature in a range from about 280 Kelvins (K) to about 320 Kelvins(K).

In an embodiment, where the flexible solid electrolyte including theinorganic-organic composite electrolyte layer and the first and secondinorganic protective layers is provided using the aerosol deposition,the aerosol deposition may include spraying powder of each component(e.g., inorganic-organic composite electrolyte layer forming material)against a target (e.g., the first inorganic protective layer) at a highspeed of from about 300 meters per second (m/s) to about 500 m/s forabout 1 second to about 100 seconds to form an intended thin film (e.g.,the flexible solid electrolyte).

Hereinafter, an embodiment of providing a flexible solid electrolyteusing aerosol deposition will be described in greater detail.

In an embodiment, to provide the first and second inorganic protectivelayers, inorganic powder having a composition of the first and secondinorganic protective layers of an embodiment of the flexible solidelectrolyte described above (e.g., at least one of a transition metal, ametal in Groups 1, 12, 13, 14, 15 and 16 of the periodic table of theelements, and compounds of the above-listed metal) may be prepared. Insuch an embodiment, the inorganic powder may have an average particlediameter in a range of, for example, from about 1 μm to about 10 μm.After synthesizing lithium conductive polymer powder as an organicelectrolyte, the organic electrolyte may be mixed with the inorganicpowder at a predetermined weight ratio to prepare mixed powder forforming an inorganic-organic composite electrolyte layer. In analternative embodiment, the mixed powder for forming theinorganic-organic composite electrolyte layer may be further mixed witha solid ionic conductor powder. The lithium conductive powder may havean average particle diameter in a range of, for example, from about 1 μmto about 10 μm.

In such an embodiment, the inorganic powder may be sprayed on anelectrode (e.g., a cathode) using an aerosol deposition apparatus toform the first inorganic protective layer. Subsequently, the mixedpowder may be sprayed on the first inorganic protective layer to formthe inorganic-organic composite electrolyte layer. Afterward, theinorganic powder may be sprayed on the inorganic-organic compositeelectrolyte layer to form the second inorganic protective layer, therebycompleting the preparation of the flexible solid electrolyte.

An embodiment of an all-solid-state lithium battery may be manufacturedusing an embodiment of the flexible solid electrolyte described above.

According to another embodiment, an all-solid-state lithium batteryincludes a plurality of flexible solid electrolytes.

In such an embodiment, the all-solid-state lithium battery includes anembodiment of the flexible solid electrolyte with improved ionicconductivity and improved flexibility characteristics, such that theall-solid-state lithium battery may have improved ionic conductivity andimproved flexibility characteristics, and thus, electrochemicalstability and energy efficiency of the all-solid-state lithium batterymay be increased.

According to an embodiment, the all-solid-state lithium battery mayinclude a cathode, an anode, and an embodiment of the flexible solidelectrolyte described above, which is disposed between the cathode andthe anode. In another embodiment, the all-solid-state lithium batterymay further include polymer electrolyte membranes disposed respectivelybetween the cathode and the solid electrolyte and between the anode andthe solid electrolyte.

In such an embodiment, where the all-solid-state lithium batteryincludes the polymer electrolyte membranes, adhesion between the solidelectrolyte and the cathode and/or anode may be improved, therebyimproving battery characteristics. In an embodiment, the polymerelectrolyte membranes may be impregnated with an organic electrolytesolution including a lithium salt and an organic solvent.

Hereinafter, an embodiment of a method of manufacturing theall-solid-state lithium battery will be described in greater detail.

First, a cathode is prepared.

In an embodiment, the cathode may be prepared by providing, e.g.,forming, a cathode active material layer including a cathode activematerial on a current collector. In such an embodiment, the cathodeactive material layer may be formed by a vapor phase method or a solidphase method. In an embodiment, where the cathode active material layermay be formed by the vapor phase method, the vapor phase method may bepulse laser deposition (“PLD”), sputtering deposition, chemical vapordeposition (“CVD”) or aerosol deposition, for example, but not beinglimited thereto. In such an embodiment, any of various vapor phasemethods available in the art may be used. In an embodiment where thecathode active material layer may be formed by the solid phase method,the solid phase method may be sintering, a sol-gel method, a doctorblade method, screen printing, slurry casting or powder compression, forexample, but not being limited thereto. In such an embodiment, any ofvarious solid phase methods available in the art may be used.

The cathode active material may be any common cathode active materialavailable in the art, for example, a lithium transition metal oxide, atransition metal oxide, or the like. The common cathode active materialmay be at least one of a composite oxide of lithium with a metal, whichinclude at least one selected from Co, Mn, Ni and a combination thereof.In one embodiment, for example, the common cathode active material maybe at least one composite oxide of lithium with a metal, which includesat least one selected from cobalt, manganese, nickel, and combinationsthereof. In one embodiment, for example, the common cathode activematerial may be a compound represented by one of the following formulae:Li_(a)A_(1-b)B_(b)D₂(where 0.90≦a≦1.8, and 0≦b≦0.5);Li_(a)E_(1-b)B_(b)O_(2-c)D_(c) (where 0.90≦a≦1.8, 0≦b≦0.5, and0≦c≦0.05); LiE_(2-b)B_(b)O_(4-c)D_(c) (where 0≦b≦0.5, and 0≦c≦0.05);Li_(a)Ni_(1-b-c)Co_(b)B_(c)D_(Dα) (where 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05,and 0<α≦2); Li_(a)Ni_(1-b-c)Co_(b)B_(c)O_(2-α)F_(α) (where 0.90≦a≦1.8,0≦b≦0.5, 0≦c≦0.05, and 0<α<2); Li_(a)Ni_(1-b-c)Co_(b)B_(c)O_(2-α)F₂(where 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, and 0<α<2);Li_(a)Ni_(1-b-c)Mn_(b)B_(c)D_(α) (where 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05,and 0<α≦2); Li_(a)Ni_(1-b-c)Mn_(b)B_(c)O_(2-α)F_(α) (where 0.90≦a≦1.8,0≦b≦0.5, 0≦c≦0.05, and 0<α<20; Li_(a)Ni_(1-b-c)Mn_(b)B_(c)O_(2-α)F₂(where 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, and 0<α<2);Li_(a)Ni_(b)E_(c)G_(d)O₂ (where 0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, and0.001≦d≦0.1); Li_(a)Ni_(b)Co_(c)Mn_(d)GeO₂(where 0.90≦a≦1.8, 0≦b≦0.9,0≦c≦0.5, 0≦d≦0.5, and 0.001≦e≦0.1); Li_(a)NiG_(b)O₂ (where 0.90≦a≦1.8,and 0.001≦b≦0.1); Li_(a)CoG_(b)O₂(where 0.90≦a≦1.8, and 0.001≦b≦0.1);Li_(a)MnG_(b)O₂ (where 0.90≦a≦1.8, and 0.001≦b≦0.1); Li_(a)Mn₂G_(b)O₄(where 0.90≦a≦1.8, and 0.001≦b≦0.1); QO₂; QS₂; LiQS₂; V₂O₅; LiV₂O₂;LiIO₂; LiNiVO₄; Li_((3-f))J₂(PO₄)₃(0≦f≦2); Li_((3-f))Fe₂(PO₄)₃(0≦f≦2);and LiFePO₄.

In the formulae above, A is selected from nickel (Ni), cobalt (Co),manganese (Mn), and combinations thereof; B is selected from aluminum(Al), nickel (Ni), cobalt (Co), manganese (Mn), chromium (Cr), iron(Fe), magnesium (Mg), strontium (Sr), vanadium (V), a rare earthelement, and combinations thereof; D is selected from oxygen (O),fluorine (F), sulfur (S), phosphorus (P), and combinations thereof; E isselected from cobalt (Co), manganese (Mn), and combinations thereof; Fis selected from fluorine (F), sulfur (S), phosphorus (P), andcombinations thereof; G is selected from aluminum (Al), chromium (Cr),manganese (Mn), iron (Fe), magnesium (Mg), lanthanum (La), cerium (Ce),strontium (Sr), vanadium (V), and combinations thereof; Q is selectedtitanium (Ti), molybdenum (Mo), manganese (Mn), and combinationsthereof; I is selected from chromium (Cr), vanadium (V), iron (Fe),scandium (Sc), yttrium (Y), and combinations thereof; and J is selectedfrom vanadium (V), chromium (Cr), manganese (Mn), cobalt (Co), nickel(Ni), copper (Cu), and combinations thereof.

In another embodiment, the common cathode active material may be LiCoO₂,LiMn_(x)O_(2x)(x=1, 2), LiNi_(1-x)Mn_(x)O_(2x)(0<x<1),Ni_(1-x-y)Co_(x)Mn_(y)O₂ (0≦x≦0.5, 0≦y≦0.5), LiFePO₄, TiS₂, FeS₂, TiS₃,or FeS₃.

The cathode active material layer may further include such a solid ionicconductor as described above (e.g., a common sulfide-based conductorand/or an oxide-based conductor), in addition to the cathode activematerial. In an embodiment, where the cathode active material layerfurther includes the solid ionic conductor, an interfacial resistancebetween the cathode and a solid electrolyte layer are substantiallyreduced, ionic conductivity in the cathode active material layer aresubstantially improved, and thermal stability of the cathode issubstantially improved.

In an embodiment, the cathode active material layer may further include,for example, a conducting agent, a binder, or the like. In such anembodiment, the conducting agent and the binder may be any materialavailable in the art for such use.

After the preparation of the cathode, a flexible solid electrolyte maybe prepared using a spraying process as described above.

Next, an anode is prepared.

The anode may be prepared in the same manner as used in the preparationof the cathode, except that an anode active material, instead of thecathode active material, is used. In an embodiment, the anode mayfurther include the solid ionic conductor described above in an anodeactive material layer.

In an embodiment, the anode active material is not limited to a specificmaterial, and may be any common anode active material used in the art.In one embodiment, for example, the anode active material may include atleast one selected from the group consisting of a lithium metal, a metalalloyable with lithium, a transition metal oxide, a non-transition metaloxide, and a carbonaceous material.

In an embodiment, where the anode active material may include the metalalloyable with lithium, the metal alloyable with lithium may be Si, Sn,Al, Ge, Pb, Bi, Sb, a Si—Y alloy (where Y is an alkali metal, an alkaliearth metal, a Group XIII element, a Group XIV element, a transitionmetal, a rare earth element, or a combination thereof except for Si),and a Sn—Y alloy (where Y is an alkali metal, an alkali earth metal, aGroup XIII element, a Group XIV element, a transition metal, a rareearth element, or a combination thereof except for Sn), for example.Here, Y may be magnesium (Mg), calcium (Ca), strontium (Sr), barium(Ba), radium (Ra), scandium (Sc), yttrium (Y), titanium (Ti), zirconium(Zr), hafnium (Hf), rutherfordium (Rf), vanadium (V), niobium (Nb),tantalum (Ta), dubnium (Db), chromium (Cr), molybdenum (Mo), tungsten(W), seaborgium (Sg), technetium (Tc), rhenium (Re), bohrium (Bh), iron(Fe), lead (Pb), ruthenium (Ru), osmium (Os), hassium (Hs), rhodium(Rh), iridium (Ir), palladium (Pd), platinum (Pt), copper (Cu), silver(Ag), gold (Au), zinc (Zn), cadmium (Cd), boron (B), aluminum (Al),gallium (Ga), tin (Sn), indium (In), titanium (Ti), germanium (Ge),phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), sulfur (S),selenium (Se), tellurium (Te), polonium (Po), or combinations thereof.

In such an embodiment, the transition metal oxide may be a lithiumtitanium oxide, a vanadium oxide, and a lithium vanadium oxide, forexample.

In such an embodiment, the non-transition metal oxide are SnO₂ andSiO_(x) (0<x<2), for example.

In such an embodiment, the carbonaceous material may be crystallinecarbon, amorphous carbon, and combinations thereof, for example. In suchan embodiment, the crystalline carbon may be graphite, such as naturalgraphite or artificial graphite that are in amorphous, plate, flake,spherical or fibrous form, for example. In such an embodiment, theamorphous carbon may include soft carbon (carbon sintered at lowtemperatures), hard carbon, meso-phase pitch carbides, sintered corks,and the like, for example.

FIG. 3 is a schematic view of an embodiment of an all-solid-statelithium battery 30. Referring to FIG. 3, an embodiment of theall-solid-state lithium battery 30 includes a flexible solid electrolytemembrane 20, and a cathode 22 and an anode 24, which are disposed onopposite surfaces of the flexible solid electrolyte membrane 20,respectively. The cathode 22 includes a cathode active material layer 22a contacting (e.g., directly disposed on) the flexible solid electrolytemembrane 20, and a cathode current collector 22 b contacting the cathodeactive material layer 22 a. The anode 24 includes an anode activematerial layer 24 a contacting the flexible solid electrolyte membrane20, and an anode current collector 24 b contacting the anode activematerial layer 24 a. Such an embodiment of the all-solid-state lithiumbattery 30 may be manufactured using a solid phase method, a vapor phasemethod, or a combination of these two methods. In one embodiment, forexample, after providing, e.g., forming, the cathode active materiallayer 22 a and the anode active material layer 24 a on the oppositesurfaces of the flexible solid electrolyte membrane 20 using a vaporphase method, a solid phase method, or a combination thereof, thecathode current collector 22 b and the anode current collector 24 b maybe provided, e.g., formed, on the cathode active material layer 22 a andthe anode active material layer 24 a, respectively, therebymanufacturing the all-solid-state lithium battery 30. In an alternativeembodiment, the anode active material layer 24 a, the flexible solidelectrolyte membrane 20, the cathode active material layer 22 a, and thecathode current collector 22 b may be sequentially deposited on theanode current collector 24 b, thereby manufacturing the all-solid-statelithium battery 30.

In an embodiment, the all-solid-state lithium battery 30 may bemanufactured by sequentially depositing the anode active material layer24 a, the flexible solid electrolyte membrane 20, the cathode activematerial layer 22 a and the cathode current collector 22 b on the anodecurrent collector 24 b using aerosol deposition.

In another embodiment of the invention, a battery pack may include aplurality of battery assemblies, each including the all-solid-statelithium battery, which may be stacked therein. Such an embodiment of thebattery pack may be used in a device that operates at high temperaturesand requires high output, for example, in a laptop computer, a smartphone, an electric vehicle, and the like.

The battery pack may have high thermal stability and improved high-ratecharacteristics, and thus may be applicable in electric vehicles(“EV”s), for example, in a hybrid vehicle such as a plug-in hybridelectric vehicle (“PHEV”), or in an electricity storage system (“ESS”)for storing a large quantity of electricity.

Due to having flexible characteristics, an embodiment of theall-solid-state lithium battery including the flexible solid electrolytemay have a roll-like shape, but not being limited thereto. In analternative embodiment, the all-solid-state lithium battery includingthe flexible solid electrolyte may have any of various structures.

Hereinafter, embodiments of the invention will be described in detailwith reference to the following example. However, the scope ofembodiments of the invention is not limited to the example.

Preparation of All-Solid-State Lithium Battery: Example

PEO having a weight average molecular weight of about 600,000 wasblended with about 0.3 mole of LiCF₃SO₃ as a lithium salt to synthesizelithium conductive polymer powder having an average particle diameter ina range from about 1 μm to about 10 μm.

Li₇La₃Zr₂O₁₂ was synthesized using a solid phase method, and was thencalcined at about 120° C. to prepare Li—La—Zr-based inorganicelectrolyte powder having an average particle diameter in a range ofabout 1 nm to about 10 μm.

The lithium conductive polymer powder and the Li—La—Zr-based inorganicelectrolyte powder were uniformly mixed using milling to obtain mixedpowder.

Li₄Ti₅O₁₂-carbon powder as an anode active material was sprayed onto aCu foil as an anode current collector using an aerosol depositionapparatus at a high speed of about 300 m/sec for about 120 seconds toform an anode active material layer.

The Li—La—Zr-based inorganic electrolyte powder was sprayed onto theanode active material layer by using the aerosol deposition apparatus ata high speed of about 300 m/s for about 10 seconds to form a firstinorganic protective layer having a thickness of about 0.1 μm.

The mixed powder was sprayed onto the first inorganic protective layerusing the aerosol deposition apparatus at a high speed of about 300 m/sfor about 120 seconds to form an inorganic-organic composite electrolytelayer having a thickness of about 1 μm.

The Li—La—Zr-based inorganic electrolyte powder was sprayed onto theinorganic-organic composite electrolyte layer using the aerosoldeposition apparatus at a high speed of about 300 m/s for about 10seconds to form a second inorganic protective layer having a thicknessof about 0.1 μm.

LiFePO₄-carbon powder as a cathode active material was sprayed onto thesecond inorganic protective layer using the aerosol deposition apparatusat a high speed of about 300 m/s for about 120 seconds to form a cathodeactive material layer.

A scanning electron microscopic (“SEM”) image of a surface structure ofthin films formed through the aerosol deposition processes as describedabove is shown in FIG. 4. Referring to FIG. 4, the thin films formedthrough the aerosol deposition processes provides a dense solidelectrolyte membrane, e.g., may have a density in a range of about 0.3gram per cubic centimeter (g/cm³) to about 1.0 g/cm³. In one embodiment,the first inorganic protective layer has a density in a range of, forexample, about 0.3 g/cm³ to about 1.0 g/cm³, the second inorganicprotective layer has a density in a range of, for example, about 0.3g/cm³ to about 1.0 g/cm³, and the inorganic-organic compositeelectrolyte layer has a density in a range of, for example, about 0.5g/cm³ to about 1.0 g/cm³.

Evaluation of the Example: Ionic Conductivity Measurement

To measure ionic conductivity of the solid electrolyte membrane preparedin above Example, the resistance of the solid electrolyte membrane wasmeasured by impedance spectroscopy using a Solartron 1260 frequencyresponse analyzer and a Solartron 1287 electrochemical interface (fromSolartron Analytical) at a frequency range of from about 1 hertz (Hz) toabout 1 megahertz (MHz). Afterward, area specific resistance wascalculated from impedance data obtained by the resistance measurement ofthe solid electrolyte membrane prepare as the Example described above,and was used to calculate ionic conductivity of the solid electrolytemembrane. The results of the ionic conductivity measurement are shown inFIG. 5.

As described above, according to an embodiment of the invention, aflexible solid electrolyte including an inorganic-organic compositeelectrolyte layer, which is protected by inorganic protective layers,may have high electrochemical stability, high ionic conductivity, andflexible characteristics. An embodiment of an all-solid-state lithiumbattery including the flexible solid electrolyte may have improvedphysical and electrical characteristics. According to an embodiment of amethod of preparing a flexible solid electrolyte, the flexible solidelectrolyte may be manufactured at room temperature by spraying, and theprepared flexible solid electrolyte may have a reduced interfacialresistance with respect to an electrode of the all-solid-state lithiumbattery.

It should be understood that the embodiments described herein should beconsidered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each embodimentshould typically be considered as available for other similar featuresor aspects in other embodiments.

What is claimed is:
 1. A flexible solid electrolyte comprising: a firstinorganic protective layer; an inorganic-organic composite electrolytelayer comprising an inorganic component and an organic component; and asecond inorganic protective layer, wherein the inorganic-organiccomposite electrolyte layer is disposed between the first inorganicprotective layer and the second inorganic protective layer, and theinorganic component and the organic component collectively form acontinuous ion conducting path.
 2. The flexible solid electrolyte ofclaim 1, wherein each of the first inorganic protective layer and thesecond inorganic protective layer comprises at least one of lithium,magnesium, calcium, strontium, barium, yttrium, lanthanum, titanium,zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum,tungsten, cerium, praseodymium, neodymium, samarium, gadolinium, andyttrium; oxides, hydroxides, bromides, chlorides, fluorides, sulfides,nitrates, carbonates, sulfates, phosphates, oxalates, acetates thereof,and ionic liquids thereof.
 3. The flexible solid electrolyte of claim 1,wherein each of the first inorganic protective layer and the secondinorganic protective layer has a thickness in a range of about 1nanometer to about 100 micrometers.
 4. The flexible solid electrolyte ofclaim 1, wherein the inorganic-organic composite electrolyte layercomprises an inorganic electrolyte, an organic electrolyte or an ionicliquid.
 5. The flexible solid electrolyte of claim 4, wherein a weightratio of the inorganic electrolyte with respect to the organicelectrolyte is in a range of about 80:20 to about 20:80.
 6. The flexiblesolid electrolyte of claim 1, wherein the inorganic-organic compositeelectrolyte layer has a thickness in a range of about 10 nanometers toabout 1,000 micrometer.
 7. The flexible solid electrolyte of claim 4,wherein the organic electrolyte comprises a polymer and a lithium salt.8. The flexible solid electrolyte of claim 7, wherein the polymercomprises at least one of polyethylene oxide (PEO),polymethylmethacrylate (PMMA), polypropylene oxide, polyvinylidenefluoride (PVDF), polystyrene, polyvinyl chloride (PVC), polyvinylalcohol (PVA), polyacrylonitrile (PVN), and polyester sulfide,derivatives thereof, and a polymer with an ionic-dissociable group. 9.The flexible solid electrolyte of claim 4, wherein the inorganiccomponent and the organic component of the inorganic-organic compositeelectrolyte layer has a core-shell structure, one of the inorganiccomponent and the organic component of the inorganic-organic compositeelectrolyte layer defines a core of the core-shell structure, and theother of the inorganic component and the organic component of theinorganic-organic composite electrolyte layer defines a shell of thecore-shell structure.
 10. The flexible solid electrolyte of claim 1,wherein the first inorganic protective layer, the second inorganicprotective layer or the inorganic-organic composite electrolyte layer isprovided using aerosol deposition such that the first inorganicprotective layer, the second inorganic protective layer or theinorganic-organic composite electrolyte layer has a density in a rangeof about 0.3 gram per cubic centimeter to about 1.0 gram per cubiccentimeter.
 11. An all-solid-state lithium battery comprising: acathode; an anode; and a flexible solid electrolyte disposed between thecathode and the anode, wherein the flexible solid electrolyte comprises:a first inorganic protective layer; an inorganic-organic compositeelectrolyte layer comprising an inorganic component and an organiccomponent; and a second inorganic protective layer, wherein theinorganic-organic composite electrolyte layer is disposed between thefirst inorganic protective layer and the second inorganic protectivelayer, and the inorganic component and the organic componentcollectively form a continuous ion conducting path.
 12. Theall-solid-state lithium battery of claim 11, wherein each the firstinorganic protective layer and the second inorganic protective layercomprises at least one of lithium, magnesium, calcium, strontium,barium, yttrium, lanthanum, titanium, zirconium, hafnium, vanadium,niobium, tantalum, chromium, molybdenum, tungsten, cerium, praseodymium,neodymium, samarium, gadolinium, and yttrium; oxides, hydroxides,bromides, chlorides, fluorides, sulfides, nitrates, carbonates,sulfates, phosphates, oxalates, and acetates thereof, and ionic liquidsthereof.
 13. The all-solid-state lithium battery of claim 11, whereineach of the first inorganic protective layer and the second inorganicprotective layer has a thickness in a range of about 1 nanometer toabout 100 micrometers.
 14. The all-solid-state lithium battery of claim11, wherein the inorganic-organic composite electrolyte layer comprisesan inorganic electrolyte, an organic electrolyte or an ionic liquid. 15.The all-solid-state lithium battery of claim 14, wherein a weight ratioof the inorganic electrolyte with respect to the organic electrolyte isin a range of about 80:20 to about 20:80.
 16. The all-solid-statelithium battery of claim 11, wherein the inorganic-organic compositeelectrolyte layer has a thickness of from about 10 nanometers to about1,000 micrometer.
 17. The all-solid-state lithium battery of claim 14,wherein the organic electrolyte comprises a polymer and a lithium salt.18. The all-solid-state lithium battery of claim 17, wherein the polymercomprises at least one of polyethylene oxide (PEO),polymethylmethacrylate (PMMA), polypropylene oxide, polyvinylidenefluoride (PVDF), polystyrene, polyvinyl chloride (PVC), polyvinylalcohol (PVA), polyacrylonitrile (PVN), and polyester sulfide,derivatives thereof, and a polymer with an ionic-dissociable group. 19.The all-solid-state lithium battery of claim 14, wherein the inorganiccomponent and the organic component of the inorganic-organic compositeelectrolyte layer has a core-shell structure, one of the inorganiccomponent and the organic component of the inorganic-organic compositeelectrolyte layer defines a core of the core-shell structure, and theother of the inorganic component and the organic component of theinorganic-organic composite electrolyte layer defines a shell of thecore-shell structure.
 20. The all-solid-state lithium battery of claim11, wherein the first inorganic protective layer, the second inorganicprotective layer, or the inorganic-organic composite electrolyte layeris formed using aerosol deposition such that the first inorganicprotective layer, the second inorganic protective layer or theinorganic-organic composite electrolyte layer has a density in a rangeof about 0.3 gram per cubic centimeter to about 1.0 gram per cubiccentimeter.
 21. A method of preparing a flexible solid electrolyte, themethod comprising: spraying a first inorganic protective layer formingmaterial on a cathode to form a first inorganic protective layer;spraying an inorganic-organic composite electrolyte layer formingmaterial on the first inorganic protective layer to form aninorganic-organic composite electrolyte layer; and spraying a secondinorganic protective layer forming material on the inorganic-organiccomposite electrolyte layer to form a second inorganic protective layer.22. The method of claim 21, wherein at least one of the spraying thefirst inorganic protective layer forming material, the spraying theinorganic-organic composite electrolyte layer forming material and thespraying the second inorganic protective layer forming materialcomprises using an aerosol deposition process.